Specific gravity of polymers

Swelling pressure due to polymer network and solvent Specific gravity of polymer Molar density of amine groups in dry network Volume fraction of polymer... 

Table D.2 Specific Gravity of Polymers (Ref Driver, W.E., Plastics Chemistry and Technology, van Nostrand Reinhold, New York, 1979, p. 46)...

Monomer conversion (79) is followed by measuring the specific gravity of the emulsion. The polymerization is stopped at 91% conversion (sp gr 1.069) by adding a xylene solution of tetraethylthiuram disulfide. The emulsion is cooled to 20°C and aged at this temperature for about 8 hours to peptize the polymer. During this process, the disulfide reacts with and cleaves polysulfide chain segments. Thiuram disulfide also serves to retard formation of gel polymer in the finished dry product. After aging, the alkaline latex is acidified to pH 5.5—5.8 with 10% acetic acid. This effectively stops the peptization reaction and neutralizes the rosin soap (80). 

Global consumption of thermoplastic mbbers of all types is estimated at about 600,000 t/yr (51). Of this, 42% was estimated to be consumed in the United States, 39% in Western Europe, and 19% in Japan. At present, the woddwide market is estimated to be divided as follows styrenic block copolymers, 48% hard polymer/elastomer combinations, 26% thermoplastic polyurethanes, 12% thermoplastic polyesters, 4% and others, 9%. The three largest end uses were transportation, 23% footwear, 18% and adhesives, coatings, etc, 16%. The ranges of the hardness values, prices, and specific gravities of commercially available materials are given in Table 4. 

This, the mass per unit volume, is a function of the weight of individual molecules and the way they pack. The hydrocarbons do not possess heavy atoms and therefore the mass of the molecule per unit volume is rather low. Amorphous hydrocarbon polymers generally have specific gravities of 0.86-1.05. Where large atoms are present, e.g. chlorine atoms, the mass per unit volume is higher and so PVC, a substantially amorphous polymer, has a specific gravity of about 1.4. 

Polar substituents such as chlorine increase the interchain forces and hinder free rotation of the polymer chain. Hence polydichlorostyrenes have softening points above 100°C. One polydichlorostyrene has been marketed commercially as Styramic HT. Such polymers are essentially self-extinguishing, have heat distortion temperatures of about 120°C and a specific gravity of about 1.40. 

The material was marketed as a fibre in 1968 jointly by the Japanese companies Unitika and Mitsubishi as A-Tell. The polymer is about 41% crystalline, and has a specific gravity of 1.34, a of 223°C and a Eg of 65°C. The fibres are somewhat silk-like in character. 

ABS has a specific gravity of 1.03 to 1.06 and a tensile strength in the range of 6 to 7.5 X 10 psi. These polymers are tough plastics with outstanding mechanical properties. A wide variety of ABS modifications are available with heat resistance comparable to or better than polysulfones and polycarbonates (noted later in this section). Another outstanding property of ABS is its ability to be alloyed with other thermoplastics for improved properties. For example, ABS is alloyed with rigid PVC for a product with better flame resistance. 

Here Ceq is the ethylene concentration equilibrium to the concentration in a gaseous phase, Kp the propagation rate constant, N the concentration of the propagation centers on the catalyst surface, Dpe the diffusion coefficient of ethylene through the polymer film, G the yield of polymer weight unit per unit of the catalyst and y0at, ype are the specific gravity of the catalyst and polyethylene. 

Fig. 8.12 Longitudinal properties of high volume fraction CNT fiber-based composites produced by various research groups and using different polymer matrices [81,77,79,82]. For [79], volume fractions are calculated assuming specific gravities of 1.2 and 1 for the matrix and fiber, respectively.

Aluminium hydroxide has a Moh hardness of about 3 and a specific gravity of 2.4. It decomposes endothermically with the release of water at about 200 °C and this makes it a very useful flame retardant filler, this being the principal reason for its use in polymers. The decomposition temperature is in fact too low for many thermoplastics applications, but it is widely used in low smoke P VC applications and finds some use in polyolefins. For these applications low aspect ratio particles with a size of about 1 micron and a specific surface area of 4-10 m g are preferred. The decomposition pathway can be diverted through the mono-hydrate by the application of pressure, and this may reduce the flame retardant effect [97]. This effect can be observed with the larger sized particles. Although it is chemically the hydroxide, it has for many years been known as alumina trihydrate and by the acronym ATH. 

Because of increased steric hindrance, the polymers of p-chlorostyrene have higher heat deflection temperatures than PS. Polydichlorostyrene (Styr-amic) has a heat deflection temperature of 120 C and a specific gravity of 1.4,... 

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